Rapid development of mobile electronics, electrical vehicles, medical devices, and other like application demands high capacity rechargeable batteries that are light and small yet provide high storage capacity and electrical currents. Lithium ion technology presented some advancement in this area in comparison, for example, to lead-acid and nickel metal hydride batteries. However, to date, lithium ion cells are mainly built with graphite as a negative active material. Graphite's theoretical capacity is 372 mAh/g, and this fact inherently limits further improvement.
Silicon, germanium, tin, and many other materials are potential candidates for replacement of graphite because of their high lithiation capacities. For example, silicon has a theoretical capacity of about 4200 mAh/g, which corresponds to the Li4.4Si phase. Yet, adoption of these materials is limited in part by substantial changes in volume during cycling. For example, silicon expands by as much as 400% when charged to its theoretical capacity. Volume changes of this magnitude can cause stresses in the electrode, resulting in fractures and pulverization of active materials, losses of electrical and mechanical connections within the electrode, and capacity fading.